Hello Guys,
New to the forum! Interest in 48M been on and off over the years. Being so late in the game transmitters are a bit hard to get hold of and unfortunately I don't have a lot of cash, anyway I found the QRP Corsette transmitter design by Dave Martin. Seeing somewhere one person built it and was getting around 1.1watts.
Not really a constructor and have very basic building skills I decided to build the unit. I had most of components except for the transistors, which I sourced on eBay and the closes inductor was 15mH.
I first built the unit on breadboard to confirm the circuit worked before soldering on to copper clad board.
Doing it this way and plugging into VSWR meter and dummy load the max output was 200mW. I removed what I believe is the low pass filter a 470pf, T50-2 and 1000pf and the output increased a slightly.
Maybe components weren't right, I started with 15mH inductor. I wound wire 59turns onto a T50-2 and got close 17.38mH yes that made a difference.
I wondered because it's built on breadboard there wasn't enough grounding. I then rebuilt and soldered onto copper cladding.
The output increased to 300mW, the Motorola BFY51 gets quite warm so I stuck a fan on to help. (Still with no LPF connected)
The only time I get more output is when connected to antenna and the most I get 500-550mW but without the filter, I don't want to leave it on for long due to no filter.
Has anyone else made one of these ?
Can anyone advise if I'm doing something wrong not to get 1watt out.
Was after putting a QRP 5 watts or less station on air
Many thanks